Identification of a pathogenic mutation in a 70-year-old woman with pityriasis rubra pilaris: when genetic diagnosis influences choice of treatment strategy.

Pityriasis rubra pilaris (PRP) is a rare dermatosis characterised by hyperkeratotic follicular papules, orange-red scaly plaques and palmoplantar keratoderma. The aetiology of the disease is in most cases unclear and treatment can be challenging. Familial cases of PRP may result from pathogenic variants in the caspase recruitment domain family member 14 (CARD14). We present a case of lifelong PRP in a 70-year-old woman, where genetic testing revealed a heterozygote missense variant c.412G>A, p.(Glu138Lys) in CARD14. Therapy with ustekinumab was initiated with remarkable effect, which improved the patient's quality of life significantly.